Update FormatCheck

[alyst]

• Updates julia-format action to v4
• Switches to JuliaFormatter v2 (JuliaSyntax-based), which may catch more issues
• Drops "format-suggest" PR label check to provide suggestions for any PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.51%. Comparing base (8b0f880) to head (7c53408).
⚠️ Report is 57 commits behind head on devel.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #296      +/-   ##
==========================================
- Coverage   72.94%   72.51%   -0.44%     
==========================================
  Files          50       53       +3     
  Lines        2218     2219       +1     
==========================================
- Hits         1618     1609       -9     
- Misses        600      610      +10     

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